Harsh: Europe's cannabis died just as the first farmers arrived

Cannabis – the source of the drug marijuana – grew wild across Europe at the end of the Stone Age, but by the time early farmers reached the continent it was vanishing. It seems Europe’s first farmers just missed out on the opportunity to cultivate cannabis and reap its benefits – including its mind-bending properties.

Researchers often use ancient pollen from archaeological deposits to work out which plants once grew in a place. However, it’s difficult to do this for cannabis, because its pollen …